This invention relates to polymer pipe seal assemblies for use in on-site waste disposal systems, such as to be cast in the side walls of a poured concrete septic tank, drop box, distribution box, and the like, and which seal assemblies are able to slideably receive a drainpipe extended therethrough.
There have been several attempts to provide plastic seals which can be cast into the walls of a poured concrete septic system component during its formation. However, certain problems have arisen with several of these attempts. U.S. Pat. Nos. 4,732,397, 4,805,920, and 5,286,040 disclose one type of pipe seal for use in concrete box walls. It is formed as a one piece unit with an integrally-formed membrane covering off the opening of its wiper seal member. However, that type pipe seal design has numerous disadvantages. One is that the user has to be very careful in removing the membrane from the operating end of the wiper seal. For example, if the wiper's operating end is at all torn or if the membrane is not properly removed (e.g., leaves a jagged edge or instead too much membrane is removed), pipe sealing problems can arise. That is, either the wiper blade will tear further and become inoperable when a pipe is inserted through it, or the membrane will not provide a good watertight seal to the inserted inlet line or drainpipe. Further, since the casting forms used to pour the concrete box walls are often installed at a slant to vertical, this type pipe seal requires the use of specific angled spacer members to assure that the seal is forced completely flat against the mating form wall. However, in the typical concrete casting operation, such precise alignment is rarely achieved, such that poured concrete is often able to undesirably seep behind that type seal's wiper member. The presence of such concrete creates significant sealing problems should a pipe ever be inserted through the wiper seal. Further yet, the commercially available embodiment made in accordance with U.S. Pat. Nos. 4,732,397, 4,805,920, and 5,286,040 include three tearaway lines, i.e., one each for a 2, 3, and 4 inch pipe. However, in actual use, those "extra" tearaway lines act as inherent built-in failure points. That is, if one of such tearaway lines does not fail from associated backfill pressure exerted against the membrane, then often another one will.
U.S. Pat. No. 4,951,914 (owned by the assignee of the subject invention) discloses a two-piece pipe seal assembly which has a primary seal body with an integrally joined wiper blade, and a separate knock-out plug member which fits within an interior groove formed in the seal body's inner wall. However, that seal has the disadvantage that two pieces are required to be produced, shipped, assembled, and used. Further, unless some thickness of concrete "flash" is present (behind the membrane) to maintain the separate knock-out member in position vis-a-vis the seal body, backfill forces can push against that knock-out member sometimes causing it to be displaced. (Reference is made to U.S. Pat. No. 4,951,914 for a description of the general use, installation and operation of such polymer pipe seal assemblies.)
The improved pipe seal assembly of the present invention overcomes these and other problems with the prior art by providing a one-piece seal member with an integrally-formed tearaway membrane that is located at a position totally remote from the operating end of the seal's frusto-conical shaped wiper member. Thus, should the tearaway membrane need to be removed to permit pipe insertion, that can be done without at all affecting the integrity of the operating, i.e., inner, end of the seal's wiper blade. Further, the tearaway membrane is formed with a gusseted pull tab and appropriately positioned score lines, whereby the membrane can be easily and accurately removed when desired. Importantly, by providing a sturdy pull tab which can be readily gripped by pliers, for example, even thicker remaining dimensions of the tearaway membrane along the score lines can be used, thereby resulting in a stronger tearaway membrane. Further yet, because of the remote positioning of the membrane, then regardless how the seal is aligned during casting (vis-a-vis the mating form wall), there is no ability during casting for concrete to ever seep behind the seal's wiper blade. Thus, the present invention is easy to use, is economical as it is formed as one piece, and yet can be made (i.e., injection-molded) as one piece because the wiper blade is mounted to the seal body by a living hinge member. This advantageous feature allows the wiper blade to be readily cast initially in an outwardly aligned position. Then, during use, it is folded into an inwardly-directed operating position able to accept both the mandrel during box casting, and thereafter sealably receive a drainpipe inserted through it.
Accordingly, it is an object of the present invention to provide a one piece pipe seal assembly having a wiper blade connected to the seal body by a living hinge member, and including an integrally-formed tearaway membrane member which seals off the seal assembly at a position remote from the wiper blade's operating end.
It is a further object of the present invention to provide a tank seal assembly that is economical in manufacture and use, and which assures that no concrete can enter behind the wiper blade during the casting process within a poured concrete box wall regardless how the seal assembly is aligned on the casting mandrel.
It is a still further object of the present invention to provide a pipe seal assembly that can be cast in place in a concrete tank wall and which has an integrally-formed tearaway membrane that is so structured as to provide a permanent watertight seal when the pipe seal is not being used to receive a drainpipe.
It is another object of the present invention to provide a pipe seal assembly that is of a design that can be used with casting mandrels from various third party seal manufacturers.
Other objects and advantages of the invention may be seen in the details of the ensuing specification.